The batch‐to‐batch variation of the potency of dog– and cat–allergen‐coated lancets

Abstract

In clinical work I formed the impression that the potency of Phazet lancets, for cat and dog allergens, was lower than earlier and too low to diagnose all clinically sensitive children with cat and dog allergy. Therefore, I decided to investigate the potency of newly produced and several years old Phazet lancets coated with dog and cat allergens. Twenty-six adults with case histories of cat and/or dog allergy and skin reactive to extracts of either dog dander or cat epithelium were skin prick tested in duplicate with one old batch and one newly produced batch of Phazet dog and/or cat lancets as well as the in-house reference of cat and/or dog allergen, 100,000 BU/ml. The potency of Phazet lancets in relation to the standard was evaluated by the median slope of the allergen dose-response relationship. The potency of the old dog lancets (mean 48,900 BU/ml) was higher (NS) than that of the newly produced lancets (mean 28,000 BU/ml), and the potency of both types of lancets was significantly less (P < 0.001) than that of the dog allergen in-house standard. On the other hand, the potency of newly produced (123,000 BU/ml), but not old (108,000), cat-allergen-coated Phazet lancets was higher than that of the cat allergen in-house reference extract (P = 0.048). There was a marked variation in potency between patients. Most of this variation was due to factors varying between patients, not between lancets, indicating that the composition of the allergen on the lancets was partly different from that of the standard.(ABSTRACT TRUNCATED AT 250 WORDS)